The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Resistive devices such as layered heaters or load resistors are typically used in applications where space is limited, when heat output needs vary across a surface, or in ultra-clean or aggressive chemical applications. A layered resistive device, such as a layered heater, generally comprises layers of different materials, namely, a dielectric and a resistive material, which are applied provides electrical isolation between the substrate and the resistive material and also minimizes current leakage during operation. The resistive material is applied to the dielectric material in a predetermined pattern and provides a resistive heater circuit. The layered heater also includes leads that connect the resistive heater circuit to a heater controller and an over-mold material that protects the lead-to-resistive circuit interface. Accordingly, layered load devices are highly customizable for a variety of applications.
Individual layers of the resistive devices can be formed by a variety of processes, one of which is a “thick film” layering process. The layers for thick film resistive devices are typically formed using processes such as screen printing, decal application, or film printing heads, among others. For each layer within the thick film resistive device, multiple coats or applications of the thick film material are often required to achieve the desired thickness. With the multiple coats, variations in the thickness of a given layer often occur, such as nonconformities along the edge of the layer. As a result, degradations in thermal uniformity, such as dielectric strength, can occur throughout the various layers and thus impact the performance of a layered resistive device.